The Mark-I Holographic Video Display

The Mark-I Full Color Holographic Video Display

The Mark-I Holographic Video Display is capable of rendering full-color

25x25x25mm images with a 15° view-zone at rates over 20 frames per

second. The holographic image is generated using a three-channel

tellurium-dioxide Acousto-Optic Modulator (AOM). A holographic fringe

pattern is sent through each channel of the AOM to modulate red (HeNe),

green (double-YAG) and blue (HeCd) light. The three resulting wavefronts

are combined using a Holographic Optical Element (HOE), to produce one

horizontal line of the horizontal-parallax-only image. To provide sufficient

resolution for the holographic diffraction pattern, each horizontal line is 32K

samples per color. Since the holographic fringe pattern in the AOM is

moving, a horizontal scanning mirror (18-sided spinning polygon) is used

to scan out the horizontal line and make the image appear stationary. A

vertical scanning mirror is used to produce 64 lines (at video resolution)

in a raster scan fashion.

Each frame of the holographic image is 6-MBytes and needs to provided
by a frame buffer as a 32K-sample horizontal by 64-line vertical signal
simultaneously for red, green and blue. We are currently using a Silicon
Graphics Onyx with an RE2 to be able to produce these patterns in this
format at near video rates. The display can be run in two modes, either
displaying pre-computed images at over 20 frames per second, or in
interactive mode updating the image at over 2 frames per second. In
interactive mode, a user can manipulate the image using several dials,
and each new 6-MByte fringe pattern is computed on the fly. User
operations include choosing new 3D objects, scaling and rotating those
objects, and changing the lighting direction.

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